The first four boys were undergoing medical checks in hospital and were not yet allowed close contact with relatives due to fear of infections.

Relatives were able to see them through a glass partition, the governor said.

Ambulances at the hospital are on standby to receive the next batch of boys who are expected to be plucked from the cave.

Medical staff involved in the rescue mission say their first assessments when the boys arrive at the hospital will focus on their breathing, signs of hypothermia and an airborne lung infection known as 'cave disease'.

The disease is caused by bat and bird droppings and can be fatal if untreated and allowed to spread to other parts of the body.

The first four rescued boys have been placed in a ward set aside specifically for the cave rescue, a source at the hospital said.

Authorities have said extracting the entire team from the cave could take up to four days.